Greylisting Addon

Paul R. Ganci ganci at
Thu Nov 29 02:33:30 GMT 2007

Michael Mansour wrote:
> DCC's greylist work fine for *non-MX* servers, however for inbound MX 
> servers which don't have local recipients (but pass the message onto 
> an internal mail server after releasing the message from the embargo), 
> DCC greylist tries to authenticate the recipients with the MX server 
> itself, which of course fails with a "user unknown" and bounces the 
> message to the sender.
> DCC greylist doesn't bother reading sendmail's mailertable to 
> determine where the destination recipient is or to even consider that 
> it's just an inbound MX server and should just greylist (embargo in 
> DCC terminology) the email and then send it on to the real mail server 
> with the inboxes.
> I explained and reported this problem to Vernon but he didn't accept 
> it as a problem, instead tried to convince me that I didn't need MX 
> servers and I should just run a beefy mail server.
> A few emails bounced between us before I gave up trying to explain to 
> him why his greylist 
I run a small ISPs Email system where we have two inbound servers with 
MX records which just forward to the server with the inboxes. I use DCC 
on both servers with greylisting enabled. I do not have the problem you 
describe ... my inbound servers do not try to authenticate users. Are 
you sure that you don't just have some kind of configuration issue? I 
watch my logs regularly and have never ever seen DCC cause a "user 
unknown" error with a subsequent bounce to the sender. I have been 
running DCC with greylisting enabled for the last two years now.
> He's a cluely guy and knows his stuff, but I just couldn't get through 
> to him, he simply didn't accept the setup I had as a valid setup. Go 
> figure.
I have had several Email exchanges with him. I agree with your 
assessment but would add that he is just a stubborn guy who believes his 
way is the only way. While I like DCC a lot if you indicate to Vernon 
that you wish to use it in a different way than he envisioned you will 
only get grief.

Paul (ganci at

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